Abstract
III-nitride-on-silicon L3 and H2 photonic crystal cavities with resonances down to 315 nm and quality factors up to 1085 at 337 nm have been demonstrated. The reduction of quality factor (Q) with decreasing wavelength is investigated. Besides the QW absorption below 340 nm a noteworthy contribution is attributed to the residual absorption present in thin AlN layers grown on silicon, as measured by spectroscopic ellipsometry. This residual absorption ultimately limits the Q factor to around 250 at 300 nm when no active layer is present.